Patent GB-1442099-A (GB)
Title: Lens blocking device hydroxy-benzylmalonic acid derivatives and their use as stabilisers for synthetic polymers
IPC: B23Q1/54
Filed: 1974-12-02
Abstract: 1442099 Blocking lenses; casting composite articles TEXTRON Inc 2 Dec 1974 [10 Dec 1973] 52077/74 Headings B3D and B3F A lens blocking device comprises a pair of wedge-shaped prism rings 70, 102, one 70 of which is held in axial alignment and rotatable contact with a base 10 and is rotatably adjustable relative to the other ring, the rings having contiguous engaging faces 80, 103 which are inclined with respect to the axis of said one ring, indicia 124, 126, 128 on each of the rings for selecting a predetermined amount of prism in diopters by rotating the rings relative to each other, indicia 132 on the base for selecting a predetermined prism axis by rotating the rings relative to the base, the rings and base defining an open ended cavity 120 terminating in an annular edge 118, the cavity being adapted to form therein a lens block when a lens blank 122 is received on the edge, and means for supplying molten metal to the cavity. The base 10, which has passages 12, 14 for cooling water 140, is formed with a central bore 16 slidably receiving a piston 18 on a mandrel 24. Springs 20 are disposed between the mandrel and head 22 of the piston. The head has passages 28, 30, 32 containing bundles of fibre optics which transmit light from a bulb through passages 46, 48, 50 in conical protrusions 36, 38 and a protrusion 40 having frusto-conical surfaces. Observation of the light transmitted from passages 46, 48, 50 is used to align the cylinder axis and optical axis of the lens blank with the device. The base rotatably supports the lower ring 70 which can be clamped in adjusted position by J-shaped members 66 mounted in slots 58, 60 in the base and engaging an annular recess 76 in the ring. The upper surface 80 of the lower ring 70 is inclined to the axis of the ring and an annular projection 82 locates the upper ring 102 with its lower surface 103 in the same plane as the upper surface of the ring 70. The upper annular edge 118, which seats the lens blank 122, is inclined to the lower surface 103. The rings have scale markings 124, 126 and 128 and can be adjusted so that the angle of the plane containing the edge 118 will increase when the inclinations of the rings are additive and vice versa. Such adjustment determines the amount of prism of the lens to be ground, and adjustment of the rings relative to a scale 132 on the base determines the position of the axis of the lens. A C-shaped ring 114 is secured to the lower ring to retain the upper ring in contact with the lower. Alternatively, a number of magnets in the lower ring may act to hold the upper ring against the lower. The rings have inner surfaces 84, 108, which, with the piston 18 and lens blank 122 define the cavity to which molten metal is supplied through a passage 56 in the piston while the blank is held on the edge 118 by a resilient pad 138, the blank engaging the projection 40 to move the piston against the pressure of the springs 20. Upon solidification, the piston is withdrawn a short distance and then returned under the force of springs 20 so as to jar the block from the device.